Epitaxially coated semiconductor wafer and process for producing it

Abstract

A semiconductor wafer with a front surface and a back surface and an epitaxial layer of semiconducting material deposited on the front surface. In the semiconductor wafer, the epitaxial layer has a maximum local flatness value SFQRmax of less than or equal to 0.13 μm and a maximum density of 0.14 scattered light centers per cm2. The front surface of the semiconductor wafer, prior to the deposition of the epitaxial layer, has a surface roughness of 0.05 to 0.29 nm RMS, measured by AFM on a 1 μm×1 μm reference area. Furthermore, there is a process for producing the semiconductor wafer. The process includes the following process steps: (a) as a single polishing step, simultaneous polishing of the front surface and of the back surface of the semiconductor wafer between rotating polishing plates while an alkaline polishing slurry is being supplied, the semiconductor wafer lying in a cutout of a carrier whose thickness is dimensioned to be 2 to 20 μm less than the thickness of the semiconductor wafer after the latter has been polished; (b) simultaneous treatment of the front surface and of the back surface of the semiconductor wafer between rotating polishing plates while a liquid containing at least one polyhydric alcohol having 2 to 6 carbon atoms is being supplied; (c) cleaning and drying of the semiconductor wafer; and (d) deposition of the epitaxial layer on the front surface of the semiconductor wafer produced in accordance with steps (a) to (c).

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]Applicant claim priority under 35 U.S.C. 119 of German Patent Application No. 199 38 340.5 filed Aug. 13, 1999. This Patent application is a division of and Applicants claim priority under 35 U.S.C. 120 of U.S. patent application Ser. No. 09 / 617,192 filed Jul. 14, 2000 now abandoned.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a semiconductor wafer with an epitaxial coating on a front surface which has improved flatness and a reduced number of light scattering centers on the epitaxial layer, and to a cost-effective process for producing it. Semiconductor wafers of this type are suitable for use in the semiconductor industry, in particular for the fabrication of electronic components with line widths of less than or equal to 0.13 μm.[0004]2. The Prior Art[0005]A semiconductor wafer which is intended to be suitable in particular for the fabrication of electronic components with line widths...

AI Technical Summary

Benefits of technology

[0019]An essential feature of the invention is that by simultaneously polishing a front surface and a back surface of a semiconductor wafer in a single polishing step, followed by the supply of an aqueous liquid containing at least one polyhydric alcohol having 2 to 6 carbon atoms, a semiconductor wafer with a high degree of flatness and a low degree of roughness is produced. The process takes place without carrying out a cost-intensive final polishing step, which adversely affects the geometry of the semiconductor wafer. This process leads to an epitaxially coated semiconductor wafer with a surface having a very small number of defects.

[0021]The end product of the process is a semiconductor wafer which has been epitaxially coated at least on the front surface. This wafer satisfies the requirements imposed on epitaxially coated semiconductor wafers as starting material for semiconductor component processes with line widths of less than or equal to 0.13 μm. Because of the high yields and the omission of the final polishing step, it has advantages in terms of lower production costs over the semiconductor wafers which are produced according to the prior art.

[0029]A polishing process which is suitable for the production of the epitaxially coated semiconductor wafers according to the invention is described for example in the German Patent Application No. 19,905,737.0. A commercially available double-side polishing machine of suitable size, e.g. a machine of the AC2000 type from Peter Wolters, can be used to carry out this process. The polishing machine essentially comprises a bottom polishing plate which can rotate freely in the horizontal plane and a top polishing place which can rotate freely in the horizontal plane, both of which are covered with a polishing cloth. A continuous supply of an alkaline polishing slurry of suitable chemical composition is present and allows abrasive polishing of semiconductor wafers, in this case silicon wafers, on both sides.

[0045]An epitaxially coated semiconductor wafer produced according to the invention, in particular a silicon wafer with an epitaxial silicon coating, fulfills the requirements for the production of semiconductor components with line widths of less than or equal to 0.13 μm. The process according to the invention has proved to be an optimum solution for the production of epitaxially coated silicon wafers having the features outlined above. The geometry requirements imposed on the starting material are minimal, which reduces the demands imposed on the preliminary processes. The good geometry which is obtained in the step according to the invention is produced even after relatively little material has been removed. By virtue of the enhanced process reliability, together with a reduced risk of fracture, it is produced in very high yields, without cost-intensive steps for local correction of the geometry, for example by plasma etching, being necessary. Also it is completely preserved on the end product according to the invention as a result of the necessity of carrying out a final polishing step being obviated. It is surprising and unexpected that the process sequence according to the invention results in a product which not only has properties superior to those of semiconductor wafers produced according to the prior art, but at the same time has significant advantages over said semiconductor wafers with regard to its production costs as a result of a final polishing step being dispensed with.

Problems solved by technology

The process takes place without carrying out a cost-intensive final polishing step, which adversely affects the geometry of the semiconductor wafer.

This process leads to an epitaxially coated semiconductor wafer with a surface having a very small number of defects.